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Full text of "Practical Organic Chemistry"

330

PRACTICAL ORGANIC CHEMISTRY

1:

ester by the Schotten-Baumann reaction, and determining the
boiling-point or melting-point ; (2) by oxidation with excess of
bichromate mixture (10 grams of K2Cr2Or in 100 c.c. dilute
sulphuric acid, i : 3 by volume). The alcohols are boiled for some
time with reflux condenser, and the product distilled, neutralised
with alkali and evaporated on the water-bath and the sodium
salts tested. Glycerol will be identified by its viscid character
and reactions (p. 106). If the alcohol is in aqueous solution, it
should first be fractionated and potassium carbonate added to
the distillate, when the alcohol will separate. Glycerol or glycol
in aqueous solution may be separated by evaporation on the
water-bath.
Aldehydes and Ketones are detected in the first instance
by: (i) Shaking with a cold saturated solution of sodium
bisulphite (see Reaction 2, p. 67). (2) Adding to the aqueous
solution j#-bromo- or /-nitro-phenylhydrazine acetate solution
(see Reaction 2, p. 70).
The aldehyde may be distinguished from the ketone by its
reducing action on alkaline copper sulphate, ammonia-silver
nitrate and by SchifPs test (see Reactions, p. 67).
Carbohydrates will char on heating, and give off water and emit
a smell of burnt sugar. The substance is tested with alkaline
copper sulphate, ammonia-silver nitrate, phenylhydrazine acetate
or Molisch's test (seep. 136). Cane-sugar will not respond to
these reactions until it has been boiled for a few minutes with a
few drops of dilute sulphuric acid and inverted (see Prep, and
Notes). Special tests may then be applied to identify the
particular sugar. A few glucosides are soluble in water, and give
the sugar reactions after boiling with dilute acid.
2. Contains Nitrogen.—First test the original solid or
liquid by heating in a hard-glass tube with soda-lime (p. 2), and
notice if the smell is that of ammonia (ammonia salt, amide or
cyanide), an amine (amine or amino-acid) or a pyridine hase
(alkaloid).
Dissolve the substance in water, add caustic soda solution and
warm.
Ammonium or amine sa/fs, if present, emit the smell of
ammonia or amine ; if the salt of an insoluble organic base is
present (amine^ alkaloid)^ it may be precipitated as a liquid or
solid. Salts of aliphatic bases and bases such as benzylamjne